1. Technical Field
The present invention relates to a semiconductor device, a method of manufacturing the semiconductor device, and a switching circuit.
2. Related Art
A high electron mobility transistor (HEMT) using a compound semiconductor can operate at higher speeds than a silicon device. Because of this feature, an HEMT can be used as a device in a high-frequency switch (referred to hereinafter as an “RF switch”). Furthermore, the increasing frequencies of high-frequency switches have led to the development of HEMTs using comb-shaped gate electrodes.
For example, Non-Patent Document 1 discloses an HEMT in which source electrodes and drain electrodes are arranged in an alternating manner, and a gate electrode is disposed between each pair of a source electrode and a drain electrode. Furthermore, the HEMT of Non-Patent Document 1 includes a source side electrode pad and a drain side electrode pad that extend in the direction of the channel length, and the source electrodes and drain electrodes are arranged between the source side electrode pad and the drain side electrode pad. In the HEMT of Non-Patent Document 1, the source side electrode pad, the source electrode, the drain electrode, and the drain side electrode pad are arranged in the channel width direction in the stated order (see Non-Patent Documents 1 and 2).    Non-Patent Document 1: OHNO Yasuo, FED review, vol. 1, No. 13, pp. 7-8, Mar. 14, 2002.    Non-Patent Document 2: ITOH Masanori et al., Oki Technical Review, Issue 203, vol. 72, No. 3, pp. 61-62, July 2005.
In the HEMT of Non-Patent Document 1, since the source side electrode pad, the source electrode, the drain electrode, and the drain side electrode pad are arranged in the stated order in the channel width direction, small leak currents occur between the source side electrode pad and the drain electrode and between the drain side electrode pad and the source electrode. A leak current also occurs between the gate electrode and the electrode pads. However, HEMTs are used as DC switches as well as RF switches, and in this case, the leak current occurring when OFF cannot be ignored. Therefore a semiconductor device with a small leak current is desired.